waterproofing and maintenance

Download Waterproofing and Maintenance

Post on 04-Apr-2015

199 views

Category:

Documents

2 download

Embed Size (px)

TRANSCRIPT

PII:S0886-7798(97)00008-4

Chapter 4 WATERPROOFING AND MAINTENANCEby WALTER GRANTZ Chesapeake Bay Bridge and Tunnel District LIONG TAN Bouwdienst Rijkswaterstaat EGON S~RENSEN COWlconsult AJS HANS BURGER DHV U.S.A. The Netherlands Denmark The Netherlands

Contributions and comments for the 1997 edition by:

Ahmet Gursoy Christian Ingerslev

U.S.A. U.S.A.

Tunnelling and UndergroundSpace Technology, Vol, 12, No.2, pp. 111 - I 24, 1997 1997 Elsevier Science Ltd. All fights reserved Printed in Great Britain 0886-7798/97 $17.00+0.00

Pergamon

Chapter 4: Waterproofing and Maintenance.,

INTRODUCTION

AND BACKGROUND

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.83,

STEEL TUNNELS Recent Joint Evolution Waterproof Joints for Immersed Tunnel Elements Closure Joints Terminal Joints Underwater Connections to Terminal Elements Constructed in Rock Seismic Joints Concrete Requirements Cathodic Protection of Steel Elements CONCRETE TUNNELS Water Leakage through the Concrete Structure Joints MAINTENANCE Experience with Leakage in Steel Shell Tunnels Leakage in Concrete Tunnels

3.1 3.2o

4.1 4.2

5.

REFERENCES

112 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY

Volume 12, Number 2, 1997

1. Introduction and BackgroundThis chapter deals with ensuring watertightness of immersed tunnels; and, specifically, with the methods used to ensure watertight integrity of immersed tunnels. Material in the chapter covers both steel shell tunnels and concrete box tunnels. For concrete tunnels, the two basic watertightness design philosophies are described. The first makes use of applied exterior steel and/or a waterproofing membrane. The second uses no exterior waterproofing layer, but rather accomplishes waterproofing by dividing the element into separate segments where concrete shrinkage-cracking can be prevented. Because steel tube tunnels are completely enclosed by a steel shell, the issue of waterproofing largely concerns the design of the joint between elements and corrosion of the steel. Development of methods for providing watertightness in joints in steel tunnels over the past decades has been largely empirical and mainly the result of incorporating the experience gained on one tunnel in the design of the next. This process is ongoing in the United States. In the European countries, however, development has centered on concrete tunnels, constructed with o r without membranes. This chapter provides information on current design practice for types of joints, membranes and watertight concrete. It seems appropriate to begin this section on watertightness with a brief history of its evolution in immersed tunnelling. The historY of subaqueous immersed tunnels has just attained its first cenlennial. In 1894, the first immersed tunnel large enough for a person to walk through was constructed. The Boston Metropolitan sewer, beneath Shirley Gut in Boston Harbor, used 15-m-long, 2.7-m-diameter elements consisting of brick and concrete, with 10-cm-thick exterior wood sheathing. Temporary wooden bulkheads were installed at both ends of each element and external flanges with rubber gaskets were provided to permit the elements to be bolted together. Thus, the first immersed tunnel used rubber-gasketted joints. In 1910, the Detroit River Railway Tunnel--considered to be the first full-scale immersed tunnel--used this same method. This tunnel was unusual by present-day standards in that it was of double-shell construction, placed on the bottom, with no concrete inside or out. The exterior concrete was then placed by tremie methods. After all the elements were in place, the tubes were accessed and the interior concrete lining was installed continuously, as a mined tunnel would be lined. The Detroit River Tunnel used rubber double-gasketted joints around each of the two tubes. The joint was made watertight by bolting it tight and then grouting the space between the two gaskets, in a manner not too unlike the Boston sewer built some 16 years previously. The shell was 9.5-mm riveted steel, lapped and ship-caulked. The next immersed tunnel was only one element long. This was the La Salle Street railroad tunnel in Chicago, constructed in 1912. The ends of the element tied directly into cofferdams. Again, the shell consisted of riveted shipcaulked and lapped construction. With the third immersed tunnel, the Harlem River Tunnel in New York, constructed in 1914, the design of the joints between tubes took a significant turn. The design no longer used a rubber gasket (perhaps because of the difficulty anticipated in mating the four tubes incorporated in these elements). Instead, it used a riveted steel liner plate closure across a square-butted joint after the exterior had been concreted with a tremie enclosure between elements. The space behind the liner plate was grouted. This method was quite successful and set the pattern for all of the immersed tunnels constructed subsequently in the U.S., until the Bay Area Rapid Transit (BART) Transbay Tunnel in San Francisco was constructed in 1970. The

BART Transbay Tunnel was the first to use the double rubber gasketted joint now commonly used in the U.S. The grouted steel liner plate detail (welded) was used on the BART Tunnel and continues to be used on almost all steel shell tunnels to this day. The Posey Tunnel, con'structed in 1928 in Oakland, California, and the Webster St. T u n n e l - - i t s near-twin, constructed in 1962--are the only concrete tunnels without a steel shell ever constructed in the United States, although the Fort Point Channel Tunnel Boston will soon be a third. Both tunnels were waterproofed with an external bituminous membrane protected with wood lagging, and both used tremie concrete joints. The Posey Tunnel was the first concrete immersed tunnel constructed as we know them today, preceded only by the Friedrichshafen pedestrian tunnel, which was built as two pneumatic caissons with the joint made in a cofferdam. The first immersed tunnel to use welding for its steel lining was the Detroit-Windsor vehicular tunnel, constructed in 1930. Only the longitudinal seams were welded; the circumferential seams were riveted, as in previous tunnels. The first all-welded steel shell was used for the elements of the Bankhead Tunnel, constructed in Mobile, Alabama, in 1940. By the time the Transbay Tunnel for San Francisco's Bay Area Rapid Transit (BART) system was designed, concrete immersed tunnels had long been constructed in Europe and Canada using single main gaskets and mobilizing the water pressures to compress the gasket. The first concrete tunnel in Europe was the Maas Tunnel of 1941, and a singleelement steel-covered concrete tunnel with rigid joints was constructed in 1944 in Japan. The first such gasketted tunnel in North America was the Deas Island tunnel, constructed in 1959 in Vancouver, British Columbia (Canada), which used an inflatable rubber gasket for the initial seal and water pressure to effect the final seal--but it was not until the Rendsburg Tunnel in 1961 that European immersed tunnels really took off. Thereafter, the Gina and Omega profiles came into prevalent use in European countries, as well as in Japan, Hong Kong, Taiwan and, recently, the People's Republic of China.

2. Steel Tunnels2.1 Recent Joint EvolutionApart from certain special considerations concerning corrosion, which are covered later in this chapter, the outer steel shell constitutes the basic waterproof enclosure of all steel tunnels. It is therefore mostly in-the joint area that refinements in design details can be made. From 1930 through 1960, the design of the joints in steel tunnels in the United States did not change very much. The method of operation during placement remained basically the same as it had been for the previous fifty years. The joint was mated and aligned and then pinned with two heavy steel pins. A form was installed on both sides of the joint and a massive tremie concrete pour was made, which completely enclosed the joint and, hopefully, sealed it sufficiently to allow the internal liner plates to be welded in place without great difficulty. This was not always the case, however, because tremie concrete is often imperfect. The joints would leak or, worse yet, the concrete would penetrate into the interior of the joint and harden, requiring a time-consuming "mining" operation to remove it. On the other hand, the tremie joint had one major benefit: it formed a rather strong structural connection between the elements. Although the gasketted joint is very effective in providing a more reliable working environment than the tremie joint for the installation of the steel liner plate, a disadvantage is that the structure of the joint became inherently weaker. The former thick tremie concrete encasement,

Volume 12, Number 2, 1997

TUNNELLING AND UNDERGROUNDSPACE TECHNOLOGY 113

which helped to tie the elements together, was no longer used. In L.~HRubberGaskets [--~x addition, in recent years the thickness of the structural interior concrete ring has been reduced, as higher strength concrete and more rout Pipe sophisticated methods of analysis have come to be used. These changes have resulted in an increasing problem with the effects of thermal expansion and contraction, causing longitudinal movements in the joints between elements and cracking and spalling of the interior finishes of the tunnel. Figure 4-1a. Joint detail for the Detroit River Tunnel (1910). No leakages have yet been traced to these movements in any of the tunnels where they have been observed (two tunnels in Hampton Roads, Va., U.S.A., and the Fort McHenry Tunnel in Baltimore, Md., U.S.A.). However, there is concern that the liner p l a t e - - t h e major line of defense against eventual deterioration of the main gaskets--might begin to leak as a result of the seasonal joint con

Recommended

View more >